Data represents information that has useful value. Data can take the form of stored information. Data storage can be in analog form. Data storage can also be in digital form.
Data can also be in digital format communicated between two nodes. When data is communicated, for example, it can be received and interpreted as a function of time. Some systems that receive communicated digitally-formatted data are based on a clock that determines when a voltage signal is sampled to decide whether a symbol in a data stream is, for example, a one or a zero.